This invention relates to a leukocyte eliminating filter and a method for manufacturing the same. More particularly, this invention relates to a cationized and hydrophilized leukocyte eliminating filter which is made from a porous film, and to the manufacturing method of such a leukocyte eliminating filter, wherein the surface of the porous film is rendered to retain (through coating, for instance) a hydrophilic polymer comprising an alkylsulfate or alkylsulfonate of primary, secondary, tertiary or quaternary amine, thereby modifying the surface of the porous film so as to cationize and hydrophilize the leukocyte eliminating filter.
It is usually conducted, on the occasion of blood transfusion, to eliminate of inactivate leukocyte through a centrifugal separation, a radiation exposure or filtration for the purpose of preventing the generation of various side reactions that may be caused as a result of blood transfusion, such as the induction of GVHD (Graft Versus Host Disease) which may be brought about--mainly due to the presence of leukocyte, or for the purpose of preventing an infectious disease that may be caused by a virus-infected leukocyte. Among them, the elimination of leukocyte by means of filtration is widely adopted as it can be executed at patient's bedside because of the reasons that the method is simple and low in cost.
It is desired in the operation of eliminating leukocyte at patient's bedside to employ a leukocyte eliminating filter which is not only excellent in leukocyte eliminating capability but also capable of performing a smooth filtration. Such a leukocyte eliminating filter can be obtained by modifying the surface of the porous film constituting the leukocyte eliminating filter. This surface modification involves, in meaning, not only to render the surface to become easily adherable by leukocyte in addition to the adjustment of pore size of the porous film for the physical elimination of leukocyte, but also to render the surface to become hydrophilic.
To render the surface of the leukocyte eliminating filter to become easily adherable by leukocyte can be achieved by cationizing the surface thereof. Because, since the surface of cell such as leukocyte is electronegatively charged, it is known that, in order to eliminate the electronegative charge, the surface of the leukocyte eliminating filter is required to have positive electric charge (U.S. Pat. No. 3,242,073; and No. 3,352,424).
Further, when the surface of the leukocyte eliminating filter is rendered to be hydrophilic, blood is allowed to pass through the filter with little resistance at the moment when blood or blood preparation is contacted with the leukocyte eliminating filter, thereby making it possible to realize a smooth filtration thereof. As one of the indexes representing the hyrophilicity of the surface of filter, there is known a method of employing the critical wet surface tension thereof (hereinafter referred simply to as CWST, which will be explained below in detail).